Mack, CO, USA
N426TF
CIRRUS DESIGN CORP SR22
The pilot reported that, while the airplane was in cruise flight, the engine suddenly lost power and then seized. During the subsequent forced landing, the airplane sustained substantial damage. Examination of the engine revealed that the crankshaft was fractured through the cheek extending from the No. 2 main bearing journal to the No. 3 connecting rod journal. The No. 2 main bearings had extruded from their crankcase positions and exhibited mechanical damage. The No. 2 main bearing support displayed signatures consistent with bearing shift. The No. 2 main bearing saddle support and several other bearing saddle supports exhibited fretting, consistent with movement between the engine case halves due to insufficient torque on the case through bolts. Maintenance logbook records showed that the Nos. 1, 2, 3, and 4 cylinders were replaced about 1 1/2 years before the accident. When maintenance personnel replaced those cylinders, they would have had to remove the nuts on the case through bolts because they also serve as hold-down bolts for the cylinders. Based on the evidence, it is likely that maintenance personnel applied insufficient torque on the case through bolts after replacing the cylinders, which led to case movement and ultimately to the No. 2 main bearings shifting and extruding, the crankshaft fracturing, and the engine seizing.
On September 23, 2013, about 1735 mountain daylight time, a Cirrus Design Corp SR22 airplane, N426TF, sustained substantial damage during a forced landing to runway 25 at the Mack Mesa Airport (C07), Mack, Colorado. The pilot reported that the engine seized during cruise flight. The pilot executed a forced landing to the airport but landed long, and ran off the end. The airplane became airborne again due to a drop off in the terrain. The pilot then attempted landing on a road and struck a ditch. The private pilot sustained minor injuries and his two passengers were not injured. The business flight was conducted under the provisions of 14 Code of Federal Regulations Part 91. Visual meteorological conditions prevailed and a Federal Aviation Administration (FAA) flight plan had been filed for the flight. The flight originated from the San Luis Valley Regional Airport, Alamosa, Colorado, about 1617, and was en route to the Ogden-Hinckley Airport, Ogden, Utah, when the accident occurred. The pilot reported that when the airplane was about 7 to 8 miles northeast of C07, at an altitude of 12,500 feet, the engine suddenly lost power and fuel flow reduced. The pilot reached to increase fuel flow, but the engine seized. He attempted to restart the engine, but it would not rotate. The pilot diverted the airplane to C07 and attempted a landing on runway 25. During the engine out landing, the airplane overran the runway. At the departure end of the runway was a large drop off and the airplane went over the drop off, becoming airborne again. The pilot continued to fly the airplane, maneuvering to avoid power lines and attempted a landing on a road. The airplane sustained damage during the landing. The airplane was equipped with a Heads Up Technologies Recoverable Data Module (RDM) that recorded flight and engine data at a 1 Hertz rate. Review of the recorded data confirmed the pilot's description of events. At 1723:39 (hhmm:ss), the airplane was at 12,190 feet pressure altitude and 82 percent engine power at 2,522 rpm. By 1727:29, the engine power had reduced to 49 percent at 2,524 rpm. Engine power was restored briefly and at 1727:41, was at 89 percent at 2,206 rpm, but then rapidly dropped to 0 percent power and 0 rpm at 17:30:00. The data further showed that the airplane came to rest at 1735:44. Subsequent to the accident, the engine was removed from the airplane for a teardown examination. The examination revealed that the crankshaft was fractured through at the cheek going from the No. 2 main bearing journal to the No. 3 connecting rod journal. The No. 2 main bearings had extruded from their crankcase positions and exhibited mechanical damage. The No. 2 main bearing support displayed signatures consistent with bearing shift. The No. 2 main bearing saddle supports and several other bearing saddle supports exhibited fretting. A review of the airplane's maintenance records showed that on April 13, 2012, the Nos. 1, 2, 3, and 4 cylinders were removed and replaced due to cracking in the injector boss area. The cylinders were replaced with new units at that time. The through case bolts adjacent to the No. 2 main bearing journal also serve as hold down bolts for cylinders 2 and 3. In order to remove the cylinders it was necessary to remove the nuts from the through bolts.
A total loss of engine power due to the failure of the engine crankshaft, which resulted from maintenance personnel’s application of insufficient torque on the engine case through bolts.
Source: NTSB Aviation Accident Database
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